I would not be at all optimistic about repairing those GPUs. And I am a strong believer in DIY repairs.
Unfortunately many things are not made to be repairable and sometimes even made to even prevent attempts to do so.
= = = =
From what I can see in the photos there has been some serious overheating. With perhaps lots of invisible damage.
And if you are able to salvage parts from one GPU to fix the other GPU (or source parts elsewhere) there is a good chance that something else will fail on the salvaged card.
I.e., the next "power up" likely to zap, melt, or otherwise cause the ruin of another component or two on the GPU. Could even be a higher risk for more damage.
Unless you wish to practice micro-soldering skills etc. I recommend just foregoing any repair attempts.
Plus you need schematics, specs, and a multi-meter to verify that any given repair/replacement was successful.
Just properly recycle the old GPUs.